Return with Void rock card. It's best to place void rock behind other allies. You need to make sure also your toads will live long enough to make this strategy work. All you need to do is to let toads be alive so Healing Return strategy would be useful with this for example Lady Wilde. Son of woods is best here as he can use his own return too for this.

Which one to choose? If the strategy has toads mainly, Driada is perfect. At level 16 she gives a +6 health buff to allies each turn. Forest mage is good when you need a health buff now, and Karas when yu are safe for now. Lady Wilde is the best healer.